Apparatus for heating the heads of ingot moulds or the gates of casting moulds



March 24, 1970 o. HEIDE I 3,502,847

' APPARATUS FOR HEATING THE HEADS OF meow MOULDS OR THE GATES OF CASTING MOULDS Filed Sept. 18, 1968 4 Sheets-Sheet 1 INVE N TOR March 24, 1970 0 H lDE 3,502,847

' APPARATUS FOR HEATING THE HEADS 0F INGOT MOULDS OR THE GATES OF CASTING MOULDS Filed Sept. 18, 1968 4 Sheets-Sheet 2 FIG.8

I N VE N TOR (hf-Tr H61 64C March 24, 1970 I o HE-IDE 3,502,847

APPARATUS FOR HEKTING THE HEADS OF INGOT MOULDS OR THE GATES OF CASTING MOULDS INVENTOR L H} Hide United States Patent 3,502,847 APPARATUS FOR HEATING THE HEADS OF INGOT MOULDS OR THE GATES OF CAST- ING MOULDS Otto Heide, Hageuer Strasse 132e,

Ennepetal-Verneis, Germany Filed Sept. 18, 1968, Ser. No. 760,525 Claims priority, application Germany, Sept. 19, 1967, 1,583,641 Int. Cl. F27b 14/06, 14/14 US. Cl. 219-426 20 Claims ABSTRACT OF THE DISCLOSURE An apparatus for heating the heads of ingot moulds or the gates of casting moulds comprises a tubular feeding jacket for fixing in the head or gate, a ceramic or ceramic lined heating hood on top of the feeding jacket, and an electrical heating element which projects into the heating hood and which is supported by a contact ring for supplying electric current to the heating element. In use, metal is poured into the mould so that it fills the mould and the feeding jacket. The heat from the heating element maintains the metal in the feeding jacket liquid while the metal in the mould solidifies, so that, as the metal in the 'mould solidifies and shrinks, liquid metal from the feeding jacket flows down into the mould to compensate for the shrinkage.

This invention relates to a device for heating the riser gates or feeder gates of casting moulds, or the heads of ingot moulds, for the purpose of keeping molten the metal in the gate orhead for a long period, so that the shrinking of the metal in the mould during solidification is compensated by supplying more liquid metal.

The formation of contraction cavities or pipes in an ingot or casting during solidification of the metal can be prevented only by keeping the metal in the gate or head liquid for a suflicient length of time. It is known, for example in casting steel, to keep the metal liquid by means of a heat insulating hood, or by electrically heating the gate or head. The moulds used for casting are equipped with special riser gates or feeder gates in which the metal is kept in the molten state, so that during solidification of the metal in the mould, more molten metal can flow into the mould to compensate for the shrinking of the casting. The number and sizes of the gates depends on the volume of the casting and consequently when making heavy castings a large number of large gates have to be used.

The object of the present invention is to provide a heating device for heating the head of an ingot mould while the ingot is solidifying, or for heating the feeder or riser gate of a casting mould during the solidification of a castmg.

According to the invention a device for heating the heads of ingot moulds or the gates of casting moulds comprises a tubular feeding jacket for fixing in the head or gate, a ceramic or ceramic lined heating hood on top of the feeding jacket, and an electrical heating element which projects into the heating hood and which is supported by a contact ring for supplying electric current to the heating element. In use, the heat generated by the heating element ensures that the molten metal in the feeding jacket is kept liquid during the solidification of the ingot or casting in the mould. The heating element may be a plasma burner or may be formed by a U-shaped carbon or graphite rod. Alternatively the heating element may be made of carbon or graphite but be made in the form of a cylinder closed at one end and having a rod projecting from the closed end of the cylinder and extending coaxially along the cylinder. The heating element penetrates downwards into the space within the heating hood. The internal volume of the heating jacket is preferably at least 7% of the volume of the mould with which the device is to be used, to ensure that sufiicient liquid metal is available and can flow into the mould during shrinkage of the cast metal as it solidifies.

To allow the device in accordance with the invention to be set up rapidly, the heating hood and the heating element may be mounted on the end of a pivoted arm. If the heating hood has previously been installed by hand on the mould, then only the heating element need be mounted on the pivoted arm. This allows the heating element to be swung out of its operative position when not needed.

A particularly simple arrangement is obtained by using as the heating element a U-shaped electric heating rod which projects inwards into the heating hood, the ends of the arms of the U-shaped heating rod being held by the contact ring to which electric power is supplied. The contact ring is mounted on the pivoted arm, which preferably consists of the current conductors themselves, which supply current to the ring.

The heating element is positioned inside the heating hood and in.use is above the level of the melt. If desired, the internal chamber of the heating hood may be separated from the chamber in the feeding jacket by an intermediate plate made of a material which is a good conductor of heat. In this case the heat is not transferred to the metal directly but indirectly through the intermediate plate. The intermediate plate screens the heating element from the molten metal, the purpose of this being, firstly to protect the heating element from gases, spattered metal and spattered slag, and secondly to protect the molten metal from the action of oxygen and from any destructive efliects deriving from the heating element.

In order to allow the intermediate plate to be installed and replaced easily, it is preferably located in the plane of contact between the feeding jacket and the heating hood. The intermediate plate may be made of graphite or carbon, and can have a ceramic coating on the surface facing the melt, to prevent any reaction between the material of the plate and the molten metal. For example, the ceramic coating preventsany carbon particles from the intermediate plate entering the melting and increasing its carbon content.

The wall of the cylindrical feeding jacket may have recesses which are open towards the intermediate plate or towards the heating hood. The heat radiated from the intermediate plate penetrates into the recesses, so that the metal in the feeding jacket is heated not only from above but also from the sides. Furthermore, the inner wall of the feeding jacket may be coated with a substance which reacts exothermally and ignites when contacted by molten metal entering the jacket. This coating prevents the metal which flows into the feeding jacket from being abruptly cooled, and keeps the metal hot until the heating element becomes fully effective. On the other hand the feeding jacket may have a wall of refractory material on the side facing the melt. Outside this refractory wall there is a stiff substance which reacts exothermally when the wall is contacted by the molten metal. The advantage of "this arrangement is that it allows the molten metal to be heated from the side without involving any change in the internal volume of the feeding jacket.

A further possibility is that the under surface of the intermediate plate and/ or the inner surface of the feeding jacket, may be coated with a substance which becomes detached from the wall during the heating process, preferably towards its end, and forms a protective coating on the surface of the melt so as to prevent the melt from cooling too rapidly. Alternatively the lower surface of the intermediate plate and/or the inner surface of the feeding jacket may be coated with a substance which dissolves into the molten metal or evolves a gas, to make it possible to introduce alloy elements into the molten metal after the latter has been poured into the mould, or the layer can be used to produce a particular atmosphere of gases in the feeding jacket.

Advantages can be obtained by controlling the heating power and the heating duration in relation to the solidification process taking place in the cast metal. For this purpose the hot junction of a thermocouple preferably is in- I serted into the feeding jacket. The voltage leads from the thermocouple are taken to an indicator and a control device for controlling the supply of power to the heating element. This arrangement ensures that heat is always supplied to the metal at a rate sufiicient to keep the head of metal in a liquid state for sufliciently long to compensate for shrinkage in the cast ingot or castpiece by flowing downwards into the mould to fill any shrinkage space. Various examples of devices in accordance with the invention will now be described with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical section through the heating hood of one example, the hood housing a heating rod;

FIGURE 2 is a plan view of a contact ring for supplying current to the heating rod in the hood shown in FIG- URE 1;

' FIGURE 3 is a vertical section along the line II-II in FIGURE 2;

FIGURE 4 is a similar view to that of FIGURE 1 but showing a further example;

FIGURE 5 is a plan view of a contact ring for the heating rod in the hood shown in FIGURE 4;

FIGURE 6 is a vertical section along the line VV in FIGURE 5;

FIGURE 7 is a vertical section through a casting mould fitted with another example of a device in accordance with the invention;

FIGURE 8 is a similar view to that of FIGURE 7 but with a different example;

FIGURE 9 is a similar view to those in FIGURES 7 and 8 but showing another example;

FIGURE 10 is a plan view of the arrangement shown in FIGURE 9; and,

FIGURE 11 shows the heating device illustrated in FIGURE 7 fitted with a system for automatically controlling the heating power.

As shown in FIGURES 1 to 3, one example has a heating hood 13 made of refractory material, in the form of a hollow cylinder closed at the top so as to form a hood, and through the top of which passes an electric heating element 14. The internal volume of the chamber 15 within the hood 13 is approximately 7% of that of the ingot or casting formed in the mould incorporating the example. The hood 13, in use, is installed in the top part of the mould, instead of the usual riser gates. The heating hood 13 is open at the bottom, i.e. towards the molten metal in the mould. The electric heating element 14 consists of a rod in the form of a cylindrical tube closed at its lower end and longitudinally slotted all the way to near the bottom by a slot 16 cut right across the tube. The heating element 14 can be fed with either direct or alternating current. Alternatively there can, if desired, be three longitudinal slots, so that the heating element 14 can be fed with 3-phase current.

The two arms 17, 18 formed by the slot 16 in the heating element project above the top of the heating hood 13, where they are surrounded by a contact ring 19 which is made in two parts with an electrically insulating layer 23 between them (see FIGURE 2). The two semi-circular halves of the contact ring 19 are designated 21 and 22, and each has a cooling chamber 24 with connections 25 for the circulation of water. Each half ring 21, 22 also 1 has a connection 26 for the electric current. The external diameter of the upper part of the heating element 14 corresponds to the internal diameter of the circular opening 27 in the contact ring 19, so that the heating element 14 is a fit between the two half rings 21, 22, and they are arranged so that the arm 17 of the heating element makes electrical contact with the half ring 22, and the arm 18 makes electrical contact with the half ring 21. In those cases where 3-phase current is used and the heating ele ment has three slots, the contact ring must also be in three parts.

The heating element 14 within the chamber 15 is covered externally by an electrically insulating layer 28, to prevent any possible electrical contact between the heating element 14 and the molten metal in the mould. This insulating layer 28 is made of a ceramic material with a high melting point, for example zirconium or aluminium oxide, and can be applied to the heating element 14 in the form of a slurry, which is then dried or baked. Alternatively instead of a coating 28 an insulating sheath can be used.

FIGURES 4 to 6 show the heating hood 13 of another example, and in this case the heating element which projects through the top of the cylindrical hood 13 consists of a cylindrical body 29 containing a core electrode 31 connected at its bottom to the body 29 but separated along its length by a gap from the outer body 29. Here again the heating element 29, 31 projects above the top of the heating hood 13. Electric current is supplied to the element 13 through a contact ring placed round the projecting part of the element. The contact ring is split horizontally into two annular parts 32 and 35 which are separated electrically by an insulating ring 34. The two parts 32 and 35 have cooling chambers 33 and 36 respectively. The outer part 29 of the heating element makes contact with the lower part 3 2 of the contact ring, and the central electrode 31 makes contact with the upper part 35. The

contacting surfaces are conical, as shown in FIGURES 4 to 6, but may be cylindrical as shown in the example of FIGURES 1 to 3.

FIGURE 7 shows an example of a heating device in accordance with the invention installed in the riser gate of a casting mould. The heating device consists of a cylindrical feeding jacket 38 embedded in the material of the mould 37, and a heating hood 39 the upper part of which projects above the upper surface of the mould 37. The inner chamber of the heating hood 39' is dome-shaped. In the plane of contact between the two parts 38 and 39 there is an intermediate plate 41, of graphite or carbon, which divides the internal chamber of the device into two parts. The under surface of the intermediate plate 41 is coated with a ceramic layer 42. The heating element 14 of the device penetrates downwards into the upper chamber, its upper end projecting above the top of the heating hood 39. The upper end of the heating element 14 is held in an electrical contact ring 19. In this example the heating element cannot come into contact with any molten metal in the mould 37, due to the presence of the intermediate plate 41, and therefore is not coated with an insulating layer, as are the elements shown in FIG- UREJS 1 and 4.

In operation of the mould 37, when molten metal is poured through the feeder gate 43, the molten metal rises from the interior 44 of the mould 37 into the lower chamber 45 below the intermediate plate 41, filling the feeding jacket 38 up to the ceramic layer 42. While the metal is rising in the feeding jacket 38, electric current is supplied to the heating element 14, through the ring 19. The heat radiated from the heating element 14 reaches the intermediate plate 41 both directly and by reflection from the wall of the heating hood 3 9. The intermediate plate 41, absorbs the heat and transfers it to the molten metal. The heat is initially transferred by convection, but when the molten metal begins to solidify, and the surface of the. melt becomes lower, the heat is transferred from the in termediate plate 41 to the surface of the metal in the feeding jacket 38 by radiation. The heat transferred this way keeps the metal in the liquid state, and consequently the metal flows continuously into the interior 44 of the mould as the metal in the mould solidifies and thus shrinks, thus compensating for the shrinkage. The volume of the lower chamber 45 within the feeding jacket 38 is such that by the time all the metal has solidified in the mould the chamber 45 is almost empty.

The example shown in FIGURE 8 is very similar to that in FIGURE 7 except that the cylindrical feeding jacket 38 has recesses 46 which are open at the top adjacent the intermediate plate 41, so that heat is radiated from the plate 41, into the recesses 46. Alternatively the recesses can be entirely open at the top, so that heat is radiated directly from the heating element 14 into the recesses 46. This arrangement is particularly advantageous in those cases where the feeding jacket 38 and the heating hood 39 are both made of ceramic material. The molten metal contained in the chamber 45 during casting is thus heated not only from the top but also from the side walls, through which heat is transferred from the recesses 46.

In the examples in both FIGURES 7 and 8 instead of the ceramic layer 42 the intermediate plate 41 can if desired be coated on its lower surface with a layer of a substance which leaves the plate and enters the molten metal. The substance can be such as to prevent chemical reactions from taking place in the surface layers of the molten metal, or the substance can have the effect of decreasing the grain size of the metal.

The heating device, consisting of the feeding jacket, the heating hood, the intermediate plate and the electrical heating element, may be assembled away from the mould, the complete assembly being subsequently embedded, either entirely or partly, in the mould material which can be moulding sand for example. Alternatively however, the feeding jacket maybe embedded in the mould material, the intermediate plate and the heating hood, with its heating element, being installed just before the molten metal is poured into the mould. As a further alternative, instead of using an intermediate plate, a heat screen can be formed by introducing a inert gas into the heating hood, or the surface of the molten metal in the feeding jacket can be coated with a thin layer of molten slag, for example a slag of metal oxides and fluorides.

In the example shown in FIGURES 9 and 10 only the feeding jacket 38 is embedded in'the material of the mould 37, which in this example is moulding sand. The inner wall and the bottom surface of the feeding jacket 38 consists of a shell 47 of heat resistant ceramic material, for example corundum (A1 0 Outside the shell 47 there is a stiff mixture 48 which reacts exothermally. In this example the mixture consists of a binder and a fine grained corundum, together with iron oxide and aluminium, the whole mixed with KClO or KNO When the molten metal rises into the chamber 45 in the feeding jacket 38, the mixture 48 ignites and reacts exothermally, so that heat is transferred to the molten metal in the chamber 45. The walls 47 of the feeding jacket 38 remain standing and keep the mixture from the metal.

As shown in FIGURE 9 the heating hood '39 is positioned on top of the feeding jacket 38 and the heating element 14 is held by a contact ring 19 of the kind shown in FIGURES 1 to 3, and projects down through an opening in the hood 39. Electric leads 49 connected to the contact ring 19 are mounted to pivot about a bearing block 51, so that the heating element 14 can be swung through 90 out of its operative position in which it is shown in FIGURES 9 and 10.

In the version shown in FIGURES 9 and 10 there can if desired be used an intermediate plate, or the surface of the melt can be protected by a thin layer of slag. The substances for forming the slag layer can be introduced from above, before pivoting the heating element 14 into its operative position. Alternatively a thin layer of slag producing substances can be applied to the inner surface of the feeding jacket 38 before pouring begins. The substances used for forming the slag have a comparatively low melting point, and are melted on the surface of the feeder jacket 38 by the heat of the molten metal. The slag runs down onto the surface of the metal, on which it forms a protective layer.

Advantages are obtained by controlling the heating power supplied to the heating element and hood on the basis of the temperature of the molten metal. This temperature is determined by a number of factors, for example the pouring temperature, the diameter of the feeding jacket 38, the height of the feeding jacket 38 and of the heating hood 39, the nature of the metal, the material used in the construction of the feeding jacket 38 and the heating hood 39, the mass of metal in the feeding jacket 38 and the nature of the casting mould. The heating power can be controlled by the system of FIG. 11 as follows. A thermocouple junction 52 projects inwards through the feeding jacket 38 into the chamber of the casting mould. The thermocouple junction 52 penetrates through the wall of the feeding jacket 38 into the molten metal in the interior of the feeding jacket 38. The leads 53 from the junction 52. are led to an indicator 54, which is connected to a control device 55 which controls a transformer 56, whose secondary winding is connected to the contact ring 19 of the heating element 14.

By controlling the heating power supplied to the heating element 14, by means of a thermocouple it is possible to prevent over heating of the molten metal in the feeding jacket 38, while nevertheless keeping its temperature high enough to ensure that the metal remains liquid until towards the end of the solidification, when the temperature is allowed to decrease gradually.

' secondly that there is less wastage of metal, that is to say that the metal lost in subsequently working the casting is reduced, and thirdly that cleaning operations on the feeding jacket are reduced due to its lesser volume and the reduced contact surfaces between the feeding jacket and the metal.

What is claimed is:

1. Apparatus for heating the heads of ingot moulds or the gates of casting moulds, consisting of a tubular feeding jacket for fixing in the head or gate, a ceramic heating hood mounted on top of said feeding jacket, said heating hood being provided with means defining an element receiving orifice, an electrical heating element projecting through said element receiving orifice into said heating hood, said heating element having electric terminals outside said hood, and contact ring means contacting said terminals of said heating element for supplying electric current to and supporting said heating element.

2. Apparatus in accordance with claim 1, wherein said heating element is formed by a U-shaped rod of material selected from the group consisting of carbon and graphite.

3. Apparatus in accordance with claim 1, wherein said heating element is made of material selected from the group consisting of carbon and graphite, and consists of a cylinder which is closed at one end and a rod which projects from the floor of said cylinder and extends coaxially along said cylinder.

4. Apparatus in accordance with claim 1, including a pivoted arm and means whereby said heating element is attached to said pivoted arm so that said heating element can be swung out of its operative position.

5. Apparatus in accordance with claim 4, wherein said pivoted arm is formed by electrical conductors connected to said contact ring means for supplying current to said contact ring.

6. Apparatus in accordance with claim 1, wherein said contact ring is water cooled.

7. Apparatus in accordance with claim 1, including a heat insulating sheath mounted on the part of said heating element which projects into said heating hood.

8. Apparatus in accordance with claim 1, including a heating conducting intermediate plate separating the interior chamber defined by said heating hood from the interior chamber defined by said feeding jacket, said heating element being situated in said interior chamber defined by said heating hood above said intermediate plate.

9. Apparatus in accordance with claim 8, wherein said intermediate plate is positioned in the plane of contact between said heating hood and said feeding jacket.

10. Apparatus in accordance with claim 8, wherein said intermediate plate is made of graphite or carbon.

11. Apparatus in accordance with claim 8, wherein said intermediate plate is provided with a lower surface which in use faces towards the metal in a mould, and said lower surface is provided with a ceramic coating.

12. Apparatus in accordance with claim 1, wherein the wall of said tubular feeding jacket is provided with means defining recesses which are open towards said heating hood.

13. Apparatus in accordance with claim 1, wherein the inner surface of said tubular feeding jacket is provided with a coating of a substance which reacts exothermally and ignites when molten metal flows into said feeding jacket.

14. Apparatus in accordance with claim 8, wherein the lower surface of said intermediate plate is provided with a coating of a substance which reacts exothermally and ignites when molten metaal flows into said feeding jacket.

15. Apparatus in accordance with claim 1, wherein said tubular feeding jacket comprises refractory shell means forming the inner surface of feeding jacket which in use contacts the molten metal, and a stiff mixture outside said shell, said stiff mixture reacting exothermally when molten metal flows into contact with said shell.

16. Apparatus in accordance with claim 1, wherein the inner surface of said tubular feeding jacket is provided with a coating of a substance which in use becomes detached from said inner surface and forms a coating on the surface of the molten metal to prevent too rapid cooling.

17. Apparatus in accordance with claim 8, wherein the lower surface of said intermediate plate is provided with a coating of a substance which in use becomes detached from said lower surface and forms a coating on the surface of the molten metal to prevent too rapid cooling.

18. Apparatus in accordance with claim 1, wherein the inner surface of said tubular feeding jacket is provided with a coating of a substance which in use reacts to make it possible to introduce alloy elements into the molten metal.

19. Apparatus in accordance with claim 8, wherein the lower surface of said intermediate plate is provided with a coating of a substance which in use reacts to make it possible to introduce alloy elements into the molten metal.

20. Apparatus in accordance with claim 1, further comprising a'thermocouple for measuring the temperature in said feeding jacket, a control device for controlling the heating-power of said heating element in relation to the temperature measured by said thermocouple, means whereby the hot junction of said thermocouple projects into the interior of said feeding jacket, an indicator device, and voltage leads for said thermocouple, said voltage leads connecting said thermocouple through said indicator to said control device.

References Cited UNITED STATES PATENTS 1,458,430 6/1923 Millner 2l9421 1,680,718 8/1928 Abbott 2l9-421 2,851,579 9/1958 Pfeiffer 219-427 3,057,936 10/1962 Hill l3-25 3,281,517 10/1966 Hemmer et al. l33l 3,293,412 12/1966 Profitt et al. 219-421 VOLODYMYR Y. MAYEWSKY, Primary Examiner US. Cl. X.R. 

